Electron multiplier tube



June 1941. R. c. HERGENROTHER ,2 6,17

ELECTRON MULTIPLIER TUBE Filed July 8, 1957 INVENTOR vi C. HERE. OTHER B ATTORNEY Patented June 17, 1941 ELECTRON MULTIPLIE I R TUBE V Rudolf C. Hergenrther,(Beechhurst, N. Y., assign. "or to Hazeltine Corporation, a corporation of D el aware Application July 8, 1937, Serial Nb. 152,457

- 13Clair'ns'. tel. 250-175) This invention relates to electron multiplier tubes and, more particularly,to such tubes in which the focusing or guiding of the. secondary electrons to the collector anode is accomplished entirely by the electrostatic field due to the main electrode alone. .7

Electron multiplier tubes generally comprise a cathode of any desired type for emitting, primary electrons, such as a thermionic or photosensitive element, a collector anode, at least one, but usually a plurality, of auxiliary electrodes having the property of high secondary electron emission and disposed serially between the cathode and the collector anode and'electromagnetic or electrostatic means for focusing or guiding the electrons from each electrodeto the successive electrode and finally to the collector anode. The electrodes are energized at such relative potentials that, when electrons emitted from any electrode of the tube impinge upon a subsequent auxiliary electrode, a relatively larger number of secondary electrons are emitted therefrom.

These secondary electrons are guided to, or focused upon, the succeeding electrode, the anode serving to collect the electrons emitted by the final auxiliary electrode. ,Heretofore, electron multiplier tubes havegenerally required intense electromagnetic or electrostatic fields to. confine the streams of electrons from the several electrodes to their properpaths and to prevent a relatively large numberof primary electrons from the cathode and secondary electrons from auxiliary electrodes near the cathodefrom passing directly to the collector anode Without impinging upon the successive auxiliary electrodes and thus to ensure the maximum. multiplying action. The chief defect of previous types of electron multiplier tubes is their focus requirement; that is, not only must the secondary electrons be drawn away from the multiplier electrode, but they must also be guided to the next electrode withina relatively limited area.

It i an object of the present invention, therefore, to provide an improved electron multiplier tube in which the guiding or focusing of the electron stream from each of the several emitting electrodes to the successiveelectrode is accomplished solely by the electrostatic field due to the operating potentials of the electrodes themselves and which, at the same tim.e,-pr ovides an, amplification approaching the theoretical maximum. In accordance with the present invention, an electron-multiplier tube comprises an electronemissiveelectrode, a collector anode, and one or more auxiliary electrodes having the property of high secondary emission. Each of the auxiliary electrodes consist of a structure extend;- ing transversely across the tube and including a series of closely-spaced strip-like elements of a substantial dimension axial of the tube andinclined with respect to, the axis of the tube. The auxiliary elements are so disposed between the electron-emissive electrode and anode, in relation to their normal operating potentials, that each auxiliary electrode intercepts a major portion of the electron emission from the preceding electrode and provides an unobstructed path for the fiow of secondary electrons emitted thereby to the succeeding electrode of the tube.

For a better understanding of the invention, together with other and further objects thereof, refercnceis had to the following specification taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. 7 v w H In the drawing, Fig. 1 is a diagrammaticyiew of an electron multiplier tube embodying the present invention; Fig. 2 is a perspective View of one of the auxiliary econdary electron emi-t ting electrodes of the tube of Fig. 1; and Fig, 3 is a diagrammatic view of a modified form of an electron multiplier tube embodying the present invention. i H a v Referring now more particularly to Fig. 1 of the drawing, there is shown an electron multi-. plier tube which comprises an evacuated envelope I0 having disposed therein, in the order named, an indirectly heated thermionic cathode l I, a control grid I 2, a plurality of auxiliary electrodes l3, l4, and I5, a suppressor grid I 6, and a collector anode I1. Each of the electrodes lii, l4,

and I5 extends transversely across the tube and is preferably of a louvre construction such as is shown in Fig. 2 and comprises a plurality of closely-spaced inclined slats or strip-like elements l8 supported from a yoke or frame I9 so as to slant at an angle of approximately 45 degrees with respect to the axisof the tube and thus having a substantialdimension axial of the tube. The auxiliary electrodes is, M, 1-5 are spaced at intervalsbetween the cathode H and the anode I1 and the; lectron-emissive surfaces of adjacentones of the electrodes I 3, t4, and 15 are inclined in opposite directions. These electrodes may be stamped from sheet metal stock, thus providing an integral,.-'easilymanufactured, and inexpensive electrode, I The rlower 'surfaces of the slats" I8 are coated with :a suitable. sub.- stance having high secondaryelectron emissivity, preferably a caesiumeoxide-silver compound 2- similar to well-known photosensitive surfaces, although other suitable electron-emissive surfaces may be used.

As thus arranged, the auxiliary electrode 13 comprises a first row of aligned electron-emitting members 18; the auxiliary electrode l4 comprises a second row of secondary electron-emitting members .I 8 substantially parallel to the first row of members, each member of the second row being opposite one of the electron-emitting members of electrode I3 and being mounted obliquely to the axis of alignment of the first row of such members; the auxiliary electrode l5 comprises a third row of such members arranged in similar manner; and the anode ll comprises a collector electrode opposite all of the secondary electronemitting members. Stated in another way, the auxiliary electrode l5 comprises a plurality of aligned, parallel secondary electron-emitting surfaces mounted in a row and opposite the anode l1, these surfaces being mounted obliquely to the axis of alignment thereof, and the auxiliary electrode [4 comprises a plurality of electron-emitting members l8 opposite the aforesaid surfaces and substantially parallel thereto. r

The several electrodes of the tube are adapted to be energized by operating potentials from any suitable source. For example, the several electrodes may be connected to suitable taps on a voltage divider resistor 20 so that the potential on the control grid is negative with respect to that of the cathode and the electrodes 13, i4, i5, and I! are energized at successively higher potentials. The suppressor grid l6 operates in-a conventional manner to suppress secondary electron emission from the anode ll. A leak resistor 21 may be included in the input or grid circuit, while a load resistor 22 may be included in the output circuit of the tube to develop, amplified signals for utilization in any desired manner.

'In the operation of the tube shown in Fig. 1, primary electrons are emitted from the cathode H and flow in the direction of the anode H, the intensity of the electron stream being under the control of the grid I2 to which a desired signal voltage may be applied. Due to the arrangement of the auxiliary electrodes l3, l4, and "[5, with relation to their normal operating potentials,

each auxiliary electrode divides the-electron emission from the cathode ll into'a plurality of discreteblecitron; streams and substantially obstructs or physically'blocks the major portion of any free or direct path from the preceding electrode to the succeeding electrode,'that is,- be- 2' tween alternate electrodes, so that a major portion of the electron stream from each electronemitting electrode is intercepted by the successive auxiliary electrode which thereupon emits a relatively larger number of secondaryelectrons. At the same time, a substantially direct and-uh obstructed path is provided between adjacent electrodes so that the flow of the secondary electrons to the succeeding electrode is not onlyun- I impeded but assisted by the electrostatic field therebetween." The electron stream from the cathode I l' is thus divided into a'plurality of discrete electron streams by the electrodes l3, l4 and I5 and each electrode directs these discrete electron streams upon successive ones of -the auxiliary electrodes, whereby substantially all. of the'electrons strike some part of each, auxiliary electrode'regardless of the degree of focusing of discrete electron streams upon corresponding portions of succeeding auxiliary electrodes. The

course, not a regular one or necessarily a linear one, the broken line being intended to indicate the general path of electron travel.

' In'Fig. 3 there is illustrated an electron multiplier tube embodying a modified form of the invention. In place of the thermionic cathode and controlgrid included in the tube of Fig. 1, there is provided a photocathode 23 having a structure similar to that of each of the electrodes I3, l4, and l5 of Fig. 1. The lower surfaces of the electrode-23 are photosensitive. Light rays from a suitable source, indicated by a lamp 25, may be focused on the electrode 23 by means of a suitable lens system 24, thereby to effect the emission of photoelectrons. The flow of primary and secondary electrons through the tube is thereafter. substantially the same as described with reference to Fig. 1. Here, however, the secondary emitting electrodes I30, Ma, and l5a are arranged in a slightly modified manner; that is, all of the slats or elements of the electrodes are inclined in the same direction and corresponding'elements of the several electrodes are in alignment, As in the arrangement of Fig. 1., a substantially unobstructed-path is provided for the flow of electrons between adjacent electrodes, while no direct or unimpeded path exists for the flow of electrons between alternate electrodes.

The operation of the embodiment of the tube shown in Fig. 3 is substantially the same as that of Fig. 1. The operating potential supplies and 'theinput and output circuit connections may be similar to those of Fig.1 or may be modified to suitthe application to which the tube is made.

-While there have been described what are at present considered to be the preferred embodiments of this 'invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and'modifications as fall within the true spirit and scope-of the invention.

What is claimed is: i

1; An electron multiplier tube comprising an electron-emissive electrode, a collector anode, and one or more auxiliary electrodes having the property of high secondary electron emission, each of said auxiliary electrodes consisting of a structure extending transversely across the tube and havinga series of closely spaced strip-like elements of a substantial dimension axial of the tube and inclined with respect to the axis of the tube, said auxiliary electrodes being so disposed between said electron-emissive electrode and anode, in relation to their normal operating potentials; that each auxiliaryelectrodeintercepts a major portion of the electron emission from the'preceding electrode and provides an unobstructed path'for the fiow of secondary electrons emitted'thereby to the succeeding electrode of the tube.

2. An electron multiplier tube comprising an electronj-emissiveelectrode, acollector anode,

and one or more auxiliary electrodes having the property of high secondary electron emission, each of said auxiliary electrodes consisting'of a structure extending transversely. across the tube and ,havingaseries of closely spaced strip-like elements ofv a substantial dimension axial of the tube'and inclined --with.respec't to the axis ofthe tube, said auxiliary. electrodes being so disposed between .said electron-,emissive electrode. and anode, in relation to their. normal operating po-,- tentials, that each auxiliary electrode intercepts a major'portionv of the electronemission from the preceding electrode and provides an unobstructed path forthe flow of. secondary electrons emitted thereby to, the succeeding electrode of the tube, and a suppressor electrode disposed between said auxiliary electrodes and saidanode and adapted to be maintained at a potential which is negative relative to the normal operating potential of said anode, s

3. An electron multiplier tube comprisingan electron-emissive electrode, a collector anode, and oneor more, auxiliary electrodes having the property of. high secondary electron emission, each of said auxiliary electrodes consisting of a structure extending, transversely across the tube and having a series of closely spaced strip-like elements of a substantial dimension axial ofthe tube and inclined with respect to the axis fof the tube, said auxiliary electrodes being so diSDOSed between said electron-emissive electrode and anode, in relationto-their normaloperating potentials, that each auxiliary electrode intercepts a major portion of the electron emission from the preceding electrode and provides an unobstructed path for thefiowof secondary electrons emitted thereby to the succeeding electrode of the tube, and a control grid disposed between said electron-emissive electrode and said auxiliary electrodes for controlling the intensity of the electron stream.

4. An electron multiplier tube comprising an electron-emissive electrode, a collector anode, and one or more auxiliary electrodes having the property of high secondary electron emission, each of said auxiliary electrodes consisting of a structure extending transversely across the tube and having a series of closely spaced strip-like elements of a substantial dimension axial of the tube and inclined with respect to the axis of the tube, said auxiliary electrodes being so disposed between said electron-emissive electrode and' anode, in relation to their normal operating potentials, that each auxiliary electrode intercepts a major portion of the electron emission from the preceding electrode and provides an unobstructed path for the flow of secondary electrons emitted thereby to the succeeding electrode of the tube, said electrodes and anode being adapted to be energized at progressively higher operating potentials.

5. An electron multiplier tube comprising an electron-emissive electrode, a collector anode, and one or more composite auxiliary electrodes, each of said auxiliary electrodes consisting of a louvre extending transversely across the tube and comprising a plurality of closely spaced elements having parallel surfaces inclined with respect to the axis of the tube and having the property of high secondary electron emission, said auxiliary electrodes being so disposed between said electron-emissive electrode and anode with said surfaces so arranged in relation to their normal operating potentials that each auxiliary electrode intercepts a major portion of the electron emissionnom the prec din elec ode and o ides an unobstruc ed at f thefiQ o c nda y lectr ns emit ed here to t u eedin e t ade o the tube 1 I 6-. An e ect on multi li r tube com i n an e tmmsmissive electrode a .c r-ans a and. a plu r c mposite auxi ia le trodes, each o an auxilia e e trodes nsi in Q a u re e tendin t ans ers l aprossth ube nd p nsa pluralit -closel paced e e s a ing a lle s a ss ha inathe Pr t of hi h. seconda electron, .emiss n ai electrodes bein s aced at nter al b tw n, ai electronmissive elect ode an amdethe s r a s f t elementsof said auxiliary electrodes beinginclined vvith respect to the axis of the tube, and the surfaces of the elements of adjacentelec t ode eing cl ned qp os t i ns and being so disposed, in relation to the normal operating potential thereon, that each auxiliary electrode intercepts a major portion of the electron emission irom the preceding electrode and provides an unobstructed path for the flow of secondary electrons emitted thereby to the sucseeding ele trode o the tube. I

,7. An electron multiplier tube comprising an electroneemissiye electrode, a collector anode, and a plurality of composite auxiliary electrodes, each of said auxiliary electrodes consisting of a louvre exte din t a sve se acr s e tube d 1 prising a plurality of closely spaced elements having parallel surfaces having the property of high secondary electron emission, said electrodes b ing Spaced 1 nte v s t efi .Sfli 6 91 ernissive, electmde and anode, the surfaces of the nemesi of ai a x iary electrodes being in clined with respect to the axis of the tube, and being arranged in axial alignment and so disposed, in relation to the normal operating potentials thereon, that each auxiliary electrode intercepts a major portion of the electron emission from the preceding electrode and provides an unobstructed path for the flow of secondary electrons emitted thereby to the succeeding electrode of the tube.

8. An electron multiplier tube comprising an electron-emissive electrode, a collector anode, and a plurality of composite auxiliary electrodes, each of said auxiliary electrodes consisting of a louvre extending transversely across the tube and comprising a plurality of closely-spaced elements having parallel surfaces inclined with respect to the axis of the tube and having the property of high secondary electron emission, said electrodes being spaced at intervals between said electronemissive electrode and anode and the elements of alternate electrodes being staggered with respect to the other electrodes and so disposed, in relation to the normal operating potentials thereon, that said auxiliary electrode intercepts a major portion of the electron emission from the preceding electrode and provides an unobstructed path for the flow of secondary electrons emitted thereby to the succeeding electrode of the tube.

9. An electron multiplier tube comprising an electron-emissive electrode, a collector anode, one or more auxiliary electrodes, each of said auxiliary electrodes consisting of a structure extendmg transversely across the tube and comprising a plurality of closely spaced strip-like elements inclined with respect to the axis of the tube and of a substantial dimension axial of the tube and having the property of high secondary electron emission, said auxiliary electrodes being disposed between said electron-emissive electrode and anode with said elements so arranged in-relation 'to the normal operating potentials thereonthat said auxiliary electrodes divide theelectron emission from said first-mentioned electrode into a plurality of discrete electron streams, and that each auxiliary electrode intercepts the majorportion of the electron streams from-the preceding electrode and provides an unobstructed path for the flow of secondary electrons emitted thereby to the succeeding electrode of the tube. 1

10. An electron multiplier tube comprisingan elec-tron-emissive electrode, a collector'anode; and one or more auxiliary electrodes, each'of said auxiliary electrodes consisting of a-structure extending transversely across the tube and'comprising a series of closely spaced strip-like elements'of a substantial dimension axial of the tube and having surfaces inclined withrespect to the axis of'the tube having theproperty of high secondary electron emission, said auxiliary 1 electrodes being so disposed between said electron-emissive electrode and anode that each of said auxiliary electrodes physically blocks the major portion of the direct path between the electron-emitting surface of the preceding electrode and said collector anode and provides-an unobstructed path for the flow of electrons to the succeeding electrode of the tube;

11. An electron multiplier tube comprising an electron-emissive electrode, a collector anode, and

means including a plurality of composite auxiliary electrodes proportioned physically to block the major portion of the direct path of the electron stream to the anode, each of said auxiliary electrodes consisting of a structure extending transversely across the tube and comprising a plurality of closely spaced strip-like elements of a substantial dimension axial of the tube and provided with'surfaces inclined with respect to the axis of thetube having the property of high secondary electron emission,:said auxiliary electrodes being disposed between said electronemissive electrode and anode with said surfaces so arrangedin' relation to the normal operating potentials thereon that said auxiliaryelectrodes divide the electron emission from said first-mentioned electrode into a plurality of discrete electron streams and direct them upon successive auxiliary electrodes, whereby substantially all of theelectrons strike some part of each auxiliary electrode regardless of the degree of focusing of discrete electron streams upon corresponding portions of succeeding auxiliary electrodes.

12. An electron discharge device comprising a row of aligned electron emitting members, a second row of secondary electron emitting members substantially parallel to said first row, each member in said second row being opposite one of said first electron emitting members and mounted obliquely to the axis of alignment of said first members thereof, and a collector electrode opposite all of said secondary electron emitting members. 7 a

13. An electron discharge device comprising a collector electrode, a plurality of aligned, parallel secondary electron emitting surfaces mounted in a row and opposite said collector electrode, said surfaces being mounted obliquely to the axis of alignment thereof, and a plurality of electron emitting members opposite said surfaces and subs'tantially parallel thereto.

' RUDOLF C. HERGENROTHER. 

